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在2例Kearns－Sayre综合征（KSS）和2例慢性进行性眼外肌麻痹（CPEO）患者的骨骼肌线粒体DNA（mtDNA）中发现存在单一的大片段缺失突变。缺失的长度2．5～5．5kb，突变只发生在部分线粒体DNA中，突变型mtDNA占全部mtDNA的60．5％～84．6％。在10例其它的线粒体脑肌病患者骨骼肌标本和外周血标本及数例正常骨骼肌和胎肝标本的mtDNA中均未发现缺失突变。上述发现支持mtDNA的缺失突变为KSS和CPEO主要病因的观点。
A single large fragment deletion mutation was found in skeletal muscle mitochondrial DNA (mtDNA) in two cases of Kearns-Sayre syndrome (KSS) and two cases of chronic progressive extraocular muscle paralysis (CPEO). The deletion length of 2.5 ~ 5.5kb, mutation occurs only in part of mitochondrial DNA, mutant mtDNA accounted for 60.5% to 84.6% of all mtDNA. No mutations were found in the skeletal and peripheral blood samples of 10 other patients with mitochondrial encephalomyopathy and in the mtDNA of normal skeletal muscle and fetal liver specimens. The above finding supports the notion that the deletion mutation of mtDNA is the major cause of KSS and CPEO.